Respiration is the physiologic process of providing O2 to cells to fuel metabolic processes and provides a means of expelling CO2 from the human body as a bi-product of metabolism. The effectiveness of human respiration is controlled by the availability of oxygen, a patient airway, and the tidal volume and respiratory rate of the individual. Spontaneous respiration is a function of the tidal volume of the individual and is controlled by the particular physiology of the individual based on factors such as physical condition, trauma and medication. Ambient available O2 is generally sufficient for a healthy and alert individual. However, as the individual's condition becomes impaired through disease, trauma or anesthesia, the airway may become partially obstructed and respiratory impairment may occur. As a result it may become necessary to provide supplemental O2 as well as an artificial means to maintain a patient airway to control and maintain tidal volume.
The measurement of CO2 upon expiration, including a capnogram waveform, is valuable to monitor the respiratory system. Capnography may provide information about CO2 production, pulmonary perfusion, alveolar ventilation, respiratory patterns, and elimination of CO2 from the body. Measurement of end tidal CO2 (ETCO2) may be obtained using an aspirating lumen that draws a CO2 sample at a point determined by the device used to maintain respiratory integrity.
During anesthetic management of diagnostic and therapeutic procedures, with spontaneous respiration or controlled ventilation, an airway may be utilized to prevent obstruction. In addition, trauma or other disease processes may be treated with an airway device.
Insertion and use of an airway may cause mechanical irritation of the patient's oropharynx. Upon insertion of an airway, the health care provider must navigate the structures of the oropharynx to properly position the airway. Depending on the skill of the health care provider and the particular anatomy of the patient, damage to and or irritation of the tissues may occur. It is desired to provide an airway, which by design, will promote good practice and which makes installation of the airway easier and will be better tolerated by the patient. This requires thoughtful design of the shape and dimension of the airway as well as embodiment of materials which have a smooth finish and sufficient rigidity so that insertion and the subsequent retention of tissue may be optimized.
Anesthetic management of a patient may involve spontaneous respiration. Notwithstanding this spontaneous respiration it is beneficial to maintain an unobstructed airway during sedation and spontaneous ventilation. O2 may be supplied through a nasal cannula, which may be placed as designed, or in some cases taped or wrapped around the oral airway. This supply is not optimal for a number of reasons, including availability for respiration due to physical features of the respiration flow in and around the mouth and nose. The optimal location for the release of O2 is where it will be stored and then totally inspired by the patient. This would tend to dictate locating the distal point of O2 discharge within the oropharynx.
The measurement of CO2 through Capnography is utilized as a measure of respiratory integrity of a patient undergoing anesthetized procedures or who is otherwise obtunded. The wave patterns are of primary interest and changes in these wave patterns can mean a number of things to the healthcare provider. It is helpful to the practitioner that this measurement is in and at a point in the patients' respiratory stream where the sampling of CO2 is derived in a consistent manner.
Likewise, O2 should be delivered in a manner which optimizes the saturation under low pressure oxygenation of the patient. This is accomplished through an integrated connection to O2 supply and delivered at a distal point which will optimize and utilize the structure within the oropharynx to create a volume of O2 so that saturation upon inhalation will be provided.